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  <meta charset="UTF-8">
  <title>JavaScript Const</title>
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<h2>ES2015新值：let和const</h2>
<p>通过 const 定义的变量与 let 变量类似，但不能重新赋值,无法更改原始值</p>

<p id="demo"></p>

<script>
  try{
    const PI=3.14159265358;
    PI=3.14;
  }
  catch (err){
    document.getElementById("demo").innerHTML=err;
  }
</script>
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